Why do we care about FTP?

A sprinter has to make it to the end of the race to unleash a sprint. That cannot happen without a good FTP to get them there.
A climber might be great at attacking in the anaerobic zone, recovering and doing it again - but that recovery part and the long pedals in between the fun climbing attacks are all powered by FTP.
A track endurance rider relies heavily on anaerobic capacity to power their high speed exploits, but they rely on a big aerobic capacity underneath that to keep everything together.
No matter what you ride or how you ride it, a higher FTP will make for a better day on the bike.